Rudy Giuliani conducted scathing research on his political enemies before and after he became mayor – and the records have now turned up in the city’s public archives.

David Dinkins gets blistering reviews as a hapless mayor who “never let a tennis game get in the way of tending to a tragedy, riot or fiscal upheaval.”

Fernando Ferrer, now the leading Democratic contender for mayor, is depicted as a “mediocre” politician who “stayed on the periphery of major issues, often waiting to comment long after the fact,” once he became Bronx borough president in 1987.

Ed Koch, who split with Giuliani in a famous blow-up in the mid-1990s, had the earnings of his book sales monitored around the period Giuliani was grappling with how to block Police Commissioner Bill Bratton from penning his memoirs.

Then-President Bill Clinton is blasted for failing to deliver on “false expectations” that he would help New York, instead enacting health-care reforms that “will cost New York billions.”

“BILL CLINTON IS NO FRIEND OF NEW YORK CITY!” screams the memo prepared by mayoral researchers. It also blasts the Arkansas Democrat for “an atrocious record on race relations” and criticizes him for once playing golf at an all-white club.

Rep. Charles Rangel, dean of the city’s congressional delegation, is called a “racial polarizer” whose addition to Dinkins’ 1993 re-election team is “further evidence the Mayor [Dinkins] intends [to] tear the city apart in order to win another term.”

Documents in the Municipal Archives, where Giuliani’s were shipped after he had them privately cataloged, indicate the ex-mayor compiled data on his adversaries before and after taking office.

When Ferrer was first considering a run for mayor, he held a fund-raiser at the Sheraton New York on Dec. 6, 1995. The Giuliani files include the official program from the event.

Six months later, on July 16, 1996, the mayor’s Economic Development Corp. prepared a memo describing The Bronx under Ferrer as an economic disaster.

“The Bronx has generated fewer private sector jobs during the city’s economic recovery than any other borough . . . The Bronx has the lowest ratio of jobs per resident of any other borough . . . Over 35% of personal income in the Bronx comes from welfare and other forms of public support,” the memo said.

The documents even mention Ferrer enjoys “reading spy novels, mysteries and biographies,” as well as “riding horses in the Catskills.”

Sunny Mindel, Giuliani’s spokeswoman, defended the compilations. “There’s nothing in them that wasn’t public,” she said.

Mindel said records that predate Giuliani’s taking office in 1994 apparently were mistakenly co-mingled with records and newspaper clippings routinely assembled by the mayor’s research unit.

In some cases, Giuliani’s researchers prepared briefing papers for allies outside the government.

Press aide Dwight Williams wrote a memo on June 21, 1995, to Ray Harding and Herman Badillo outlining positions on education taken by Ferrer and Ruth Messinger, the Democratic mayoral candidate who faced Giuliani in 1997.

Harding at the time was the Liberal Party leader and a key Giuliani political adviser who often appeared on TV defending the administration, as did Badillo.

Mindel argued that was proper because “Ray was almost a spokesperson on certain issues” for the administration.

An aide to Ferrer declined to attack Giuliani, saying the former Bronx borough president “considers this ancient history.”

Koch told The Post nothing Giuliani could do would surprise him anymore. “What is so interesting is that he would seek to assemble God knows what about people he might run against, but people he appointed he didn’t give a damn about – Bernie Kerik being the best example,” Koch zinged.

Dinkins was traveling and couldn’t be reached.

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Biting comments

On Dinkins: “New Yorkers have come to expect one thing of their mayor: David ‘Nero’ Dinkins often plays tennis while the city descends further downward.”

On Ferrer: “At best a mediocre politician hedging his bets for City Hall, at worst more of the machine politics he